A Random Scission Model for Chemical Degradation of Polymer Solutions

A rigorous but simple deterministic model is presented to quantify chemical degradation of high-molecular-weight polymer solutions undergoing random bond scission. Molecular-weight alteration is characterized by a fundamental rate constant, kappa, whose inverse represents the average lifetime of a polymer chain bond. Evaluation of the proposed random-scission model (RSM) against known Monte Carlo (MC) calculations shows complete agreement. Given the molecular-weight decline from the RSM, the authors establish the corresponding polymer solution viscosity loss using the semiempirical Martin equation along with the Mark-Houwink relationship for intrinsic viscosity. Comparison of the RSM viscosity predictions against the chemical degradation data of Shupe for partially hydrolyzed polyacrylamide gives good agreement. Thus, a new tool is available to predict polymer chemical degradation and viscosity loss at reservoir time scales and conditions.